This invention relates to microfilm equipment and more particularly to an improvement in microfilm duplicators which make duplicates of individual microfilm cards or microfiche.
Microfilm has become a common medium for compactly storing large amounts of information. Two types of microfilm storage are commonly used. A first is the roll film type of storage in which the images are placed on a continuous roll of microfilm usually one hundred feet long. When retrieval of a particular image is desired, the film is transported through suitable reading means until the desired image is located. A second type of storage of images on microfilm is commonly referred to as microfiche. This is commonly a four inch by six inch clear plastic envelope, or jacket, having several channels. Within the channels are placed individual strips of microfilm which contain the previously recorded images. The jacket provides a protective covering for the microfilm contained in the channels. In this format, the jacket is commonly referred to as a "master" from which duplicates are made for distribution and use. In this manner, the "master" can be maintained in a secured file which duplicates are circulated for use. Also, the "master" is not designed for constant handling and use. It can be damaged when left in one position on a microfilm reader due to overheating caused by the light passing through one image on the film. Thus it is preferable to work with a more rugged medium which has the same recorded images.
Another form of microfilm master has the images recorded in the form of relief or deformation images. The master is generally a photoplastic film which is heat deformable so as to allow for recording of deformation images. One such product presently available using photoplastic masters is sold by the assignee of the present invention under the trademark Microx. In order to simplify the discussion herein, the term "microfiche" will be used throughout to refer to jackets or microfilm masters regardless of their form.
Traditionally, duplicates of the microfiche have been made by projection of the images through lenses or by contact duplication. Duplication through use of an optical system may not be preferred, in part, because lenses are expensive and because of the space normally required to accommodate the light path. Contact duplicating from a photoplastic master may yield duplicates of inferior quality. It has been found that one can produce acceptable duplicates from such a master by projecting light from the master through a small gap onto the duplicate film. One such method is disclosed in U.S. Pat. No. 3,809,473 entitled "Method of Reproducing a Relief Image," although apparatus to implement the process is not described.
Additional apparatus for making duplicates is illustrated in U.S. Pat. No. 4,147,429 entitled "Apparatus and Process for Photographically Duplicating Intelligence Existing on Photoplastic Film." This patent goes into great detail in describing the calculation of the gap distance between the master and duplicate and illustrates apparatus to expose the duplicate to the images on the master. However, there is not illustrated any apparatus to further develop the duplicate after exposure to the master.
Contact printing or duplicating is common when the master microfiche has silver based film. Numerous contact printing devices are presently available for microfilm, but some of them are designed to only expose the duplicate creating a latent image thereon and require additional apparatus to develope the duplicate.
The duplicating media is normally hand transferred to additional processing equipment to develop the latent image and clear the portion of the duplicating media which was not imaged. Such additional processing equipment can be of various types depending upon the type of duplicating medium used.
For example, if a vesicular duplicating medium is used, the duplicating medium is first exposed to the microfiche under ultraviolet light. The developing station will generally include a conventional heat setting device to develop and set the previously exposed images. This may be followed by a clearing station wherein ultraviolet light clears the unimaged areas of the vesicular film.
If the duplicating medium is a diazo film, the images are formed by exposing the microfiche and diazo duplicating film to ultraviolet light. The exposed duplicate is then developed in aqueous ammonia systems or in anhydrous ammonia environments. Another type of diazo film which is available only requires heat for developing. A clearing station is not required with this medium.
The major drawbacks with the devices described above and those of the prior art, is that the duplicating medium must be manually moved from the exposure device to additional apparatus for processing. This is a major inconvenience to the operator and can result in developing errors should the exposed film be dropped, or affected by the atmosphere in moving it from the exposure to the developing device.